With the miniaturization of semiconductor devices, the formation of fine patterns such as contact holes with small hole diameter and high aspect ratio and the like becomes a necessity. Conventionally, contact holes and other patterns have been frequently formed by a gas plasma of c-C4F8/Ar(/O2) containing a large amount of Ar. However, cyclic c-C4F8 contributes significantly to global warming, and thus its use is likely to be limited in the future. Further, when not combined with Ar, cyclic c-C4F8 is insufficient in the resist selectivity and the silicon selectivity. The etching rate of cyclic c-C4F8 varies depending on the pattern size without the addition of a small amount of oxygen, and etching stops under fine pattern conditions. On the other hand, the addition of oxygen lowers the selectivity with regard to the resist and the silicon. It has also been reported that when an excess amount of Ar is blended, the number of high-energy electrons increases, thereby damaging devices.
An object of the present invention is to provide a dry etching gas and a dry etching method, which achieves no reduction in etching rate even when etching small-sized holes, lines or the like; little pattern-size dependency, and the formation of a fine, high-aspect-ratio pattern with no etch stopping through the use of the etching gas that has a substantially small effect on global warming.